Material is 6mm aluminium round bar, an M6x1 thread in the base and for the changeable spindles, the base is made of a large 3" scrap piece of aluminium they gave me in the tool room at work. The hole size formed by the spindle is 1.95mm, 11mm in length, and a 3+1/2" rammer with a 2mm hole drilled to a depth of 15mm, to give plenty of clearance for the 1.95mm spindle.
The tube holder (I dont really know what this bit is called, the area that is just 6mm after the thread but before the spindle) is 3.5mm long and if I made another one I'd make this a bit longer, as it doesnt hold the tube very straight, but it still works.
Fuel is normal BP + 10% metal powder, and I also have in mind using it with a weak sugar based propellant for a model plane Rapier.cz motor replacement.
I have these working with titanium sponge and they leave a great trail, with the silver sparks still visible as the rocket reaches its peak height and burns out.
